Biomedical subjects

M A Chung

Publications and source records attributed to M A Chung.

23 records · Page 2Linked to original sources

PubMed1991

An acid phosphatase as a biochemical marker for intestinal development in the nematode Caenorhabditis elegans.

We describe an acid phosphatase enzyme (EC 3.1.3.2) that is localized to the intestine of the nematode Caenorhabditis elegans and that should serve as a convenient biochemical marker for gut differentiation. In adult worms, acid phosphatase activity is located along the edge of the gut lumen in the vicinity of the intestinal brush border. All but the anterior six cells of the intestine stain for phosphatase activity; the nonstaining cells all descend from the Ea(l/r)(a/p)a cells. Acid phosphatase activity is low in oocytes and early embryos but increases substantially when embryos reach late morphogenesis stage; this increase corresponds to the appearance of a major band of acid phosphatase activity detectable on isoelectric focusing gels. We designate this band as the product of the pho-1 gene. The pattern of acid phosphatase expression in several embryonic mutants suggests that pho-1 expression in the developing intestine is lineage autonomous. We induced an isoelectric focusing variant in the pho-1 enzyme and used this to map the pho-1 locus about 1.5 map units to the left of center of chromosome II. We purified the pho-1 enzyme to homogeneity (6500-fold purification; 4% recovery of activity); the pho-1 acid phosphatase is a homodimeric glycoprotein with a subunit molecular weight of 55,000 Da. This paper establishes a new experimental system with which to investigate the molecular basis of lineage-specific gene expression during C. elegans development.

Acid Phosphatase↗

PubMed1990

Production of null mutants in the major intestinal esterase gene (ges-1) of the nematode Caenorhabditis elegans.

The ges-1 gene of the nematode Caenorhabditis elegans codes for a nonspecific carboxylesterase that is expressed only in the intestinal lineage. This esterase has turned out to be a convenient biochemical marker for lineage-specific differentiation. In the present paper, we describe the production of several C. elegans strains that lack detectable activity of the ges-1 esterase. To isolate these ges-1 null strains, we first produced a strain of hermaphrodites in which the wild-type copy of the ges-1 gene was stably balanced over a previously isolated isoelectric focusing allele, ges-1(ca6); this parental strain was then mutagenized with EMS and isoelectric focusing gels were used to identify progeny populations that lacked either ges-1(+) or ges-1(ca6) esterase activity. This method is a straightforward and general approach to obtaining null mutations in any gene that has a biochemical or immunological assay. The ges-1 gene is not essential to worm survival, development or reproduction. Furthermore, lack of the ges-1 product has no obvious effect on the ability of worms (containing either normal or greatly reduced levels of acetylcholinesterases) to survive exposure to esterase inhibitors. The ges-1 gene product provides roughly half of the total esterase activity measured in crude extracts of L1 larvae or mixed worm populations. However, histochemical staining of individual ges-1(0) embryos shows that the ges-1 esterase is the first and essentially the only esterase to be produced during embryonic development, from the midproliferation phase up to at least the twofold stage of morphogenesis. These ges-1(0) strains now allow us to investigate the developmental control of the ges-1 gene by DNA-mediated transformation, in which the ges-1 gene acts as its own reporter.

Animals↗

PubMedDate not supplied

Optimal surgical treatment of invasive lobular carcinoma of the breast.

BACKGROUND: The roles of breast conservation and surgical evaluation of the contralateral breast in the treatment of lobular carcinoma of the breast remain unclear. The aim of this study was to compare local recurrence, 5-year survival, and incidence of contralateral breast cancer in women with lobular carcinoma to that in women with infiltrating ductal carcinoma. METHODS: Women with infiltrating ductal carcinoma (IDC) and invasive lobular breast carcinoma (ILC) diagnosed during the years 1984 to 1994 were identified through a statewide tumor registry. The women were divided into groups based on their histology and treatment (breast conservation or modified radical mastectomy). The incidences of contralateral breast cancer, local recurrence, and 5-year survival were compared within each histologic group and treatment category. RESULTS: During the period 1984 to 1994, 4886 women were diagnosed with invasive lobular or ductal breast carcinoma. Of these, 316 (6.5%) had infiltrating lobular cancer. The 5-year survival rates were 68% and 71% for ILC and IDC, respectively (p = 0.5). The local recurrence rates were 2.8% and 4.3% for ILC treated with lumpectomy and axillary nodal dissection (LAND) and modified radical mastectomy (MRM), respectively, which were not significantly different from that obtained with IDC (LAND = 2.5%, MRM = 2.1%). The incidence of contralateral breast cancer during the period was 6.6% and 6.5% for ILC and IDC, respectively. CONCLUSIONS: Invasive lobular carcinoma can be safely treated with breast conservation with no difference in local recurrence or survival. In the absence of a suspicious finding on clinical or radiologic examination, routine contralateral breast intervention is not recommended.

Breast Neoplasms↗

PubMedDate not supplied

In vitro antitumor and antimicrobial activities of N-substituents of maleimide by adamantane and diamantane.

New N-1-adamantylcitraconimide (compound 1) and N-1-diamantylcitraconimide (compound 2) were synthesized by reaction of citraconic anhydride with 1-aminoadamantane, and 1-aminodiamantane, respectively, followed by imidization with acetic anhydride and sodium acetate. Compound 1, N-1-adamantylmaleimide (compound 3) and N-1-diamantylmaleimide (compound 4) exhibited strong growth-inhibitory activity against four cancer cell lines (Colo 205, Hep G2, SK-BR-3 and Molt-4). Moreover, compound 1 showed relatively specific cytotoxicity against the test tumor cell lines. Compound 2 exhibited growth inhibitory activity against Colo 205, and SK-BR-3 cells, similar to 5-fluorouracil. It was noted that compound 2 showed relatively low cytotoxicity against Molt-4 cells, approximately 42 times lower than 5-fluorouracil. The N-substituents of imides with adamantly substituents have a more potent antitumor activity than the imides with diamantyl substituents. The imides with methyl substituents (compounds 1 and 2) showed relatively higher selectivity against the tested cancer cell lines than the imides without methyl substituents (compounds 3 and 4). Compounds 3 and 4 show good in vitro activities against Staphylococcus aureus and Trichophyton mentagrophytes. Compound 1 had weak antimicrobial activity against T. mentagrophytes.

Adamantane↗

PubMedDate not supplied

Galactosemia in infancy: diagnosis, management, and prognosis.

Galactosemia is an inherited metabolic disorder in which the individual is unable to metabolize lactose. In the newborn, classic galactosemia presents with symptoms of severe feeding intolerance, malnutrition, and rapid organ damage. Without immediate treatment, the infant will almost certainly succumb to rampant disease or sepsis. Through increased clinical awareness, pediatric care providers can be better prepared to detect and manage an infant with this disorder. A multidisciplinary approach is often necessary to maintain optimal health. The nurse can play an important role in coordinating specialty services and in helping the family to manage the disease and its sequelae over time.

Developmental Disabilities↗